The present invention relates to an anti-knock additive for fuel compositions, primarily gasoline compositions.
The petroleum industry has long recognized a need for greater fuel economy and efficiency in the operation of gasoline powered spark ignition engines. In many instances, high compression ratios are desired in order to provide for superior engine performance under various driving conditions. In order to provide high performance in high compression engines without the risk of knock damage, fuels which will be used in such engines require a high octane number and good anti-knock characteristics.
While octane ratings of fuels can be improved by blending appropriate refining streams, the necessary additional refining and blending operations needed to obtain a fuel having the desired high octane rating are costly. In lieu of these various refining and blending processes the petroleum industry sometimes blends anti-knock additives into fuels to increase the octane number of the fuel. For many refineries the use of anti-knock compounds is essential due to the lack of the refining and blending facilities to produce the high octane fuels.
Numerous compounds have been suggested as anti-knock additives for fuel compositions. The most successful of these anti-knock compounds additives are organo-lead compounds. However, the future use of organo-lead compounds as anti-knock additives is severely limited by recent legislation and is completely prohibited in the future.
As a replacement for lead-containing additives, numerous non-lead, anti-knock compounds have been suggested as octane improvers. Among these are rare earth beta-keto-enolate compounds, the lithium and sodium salts of organo-amino-cresols, various other organo metallic compounds, in particular organo-iron and organo-manganese compounds, such as iron pentacarbonyl and methylcyclopentadienyl manganese tri-carbonyl. In addition, it is known to improve the anti-knock and octane properties of gasoline by blending alcohol therewith.
These anti-knock additives have their own associated problems when blended into fuels for use in internal combustion engines. The numerous organo-iron compounds increase the potential of wear in internal combustion engines and the organo-manganese compounds, in addition to causing wear problems, may affect the catalytic converters used on most cars today to reduce air pollution for exhaust emissions. Fuel compositions of gasoline and alcohol have many problems, including separation if water is admixed with the composition. As a result, there is a need for additives for increasing the octane value of gasoline without causing any detrimental effects, particularly the detrimental effects of lead, iron and other metal octane improvers or the miscibility problems of alcohol.